Strange Error messages

I was using the bbP Topic Views plugin, and it was fine; I had some other issues (speed and memory) and asked the host to migrate the site from windows to linux–and started getting the following strange errors when I clicked on a topic–even though the counting of views was still working:

Warning: session_start() [function.session-start]: open(/var/chroot/home/content/82/8351782/tmp/sess_2aorcel9g0ujkp4lkmd61nde50, O_RDWR) failed: No such file or directory (2) in/home/content/82/8351782/html/whup/wp-content/plugins/bbp-topic-views/bbp-topic-views.php on line 76

Warning: Cannot modify header information – headers already sent by (output started at /home/content/82/8351782/html/whup/wp-content/plugins/bbp-topic-views/bbp-topic-views.php:76) in/home/content/82/8351782/html/whup/wp-includes/pluggable.php on line 881

Warning: Unknown: open(/var/chroot/home/content/82/8351782/tmp/sess_2aorcel9g0ujkp4lkmd61nde50, O_RDWR) failed: No such file or directory (2) in Unknown on line 0

Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct () in Unknown on line 0